Climate change, natural disasters, and migration

The mitigating role of migration

Population movement is a natural way to deal with climatic shocks, particularly when livelihoods are destroyed. Migration can be considered as an adaptation strategy when disasters occur because it helps mitigate the adverse effects of climatic shocks by providing new opportunities and resources to affected people. It is also employed as a coping strategy when other solutions have failed. For instance, in the case of drought, potential solutions, which are also considered survival strategies, can include changing consumption patterns by reducing the number of daily meals, selling household assets, using food reserves, and benefiting from solidarity through gifts, loans, and aid. Having many possible coping strategies will reduce the likelihood of migration due to shocks [2].

Between 2008 and 2014, developing countries accounted for 95% of global displacement due to disasters. Moreover, most of the displacements are from middle-income countries (Figure 1). This is illustrative of the fact that people at the extremities of the income distribution do not necessarily migrate in the aftermath of disasters. Indeed, the poorest cannot afford to migrate and the richest have other mitigation strategies, such as the possibility to recover their lost assets or better access to effective infrastructure and social services, which allow them to cope with disasters without migrating. Therefore, people at the middle of the income distribution are those who do not have many alternatives at their disposal to deal with adverse climatic shocks and, at the same time, can afford migration costs.

However, it is important to point out that the rather low rates of disaster-related migration from poor and high-income countries does not necessarily mean that the poorest and the richest people in a specific country do not migrate. There is some heterogeneity within developing countries, which shows that the level of vulnerability and the severity of the shock also matter when it comes to the relationship between disasters and migration. The level of vulnerability is correlated with factors such as the risk of exposure to the shock, the level of poverty, the social structure, the diversification of assets and income, and the political situation. Indeed, people living in a politically unstable environment have fewer survival strategies available to them than those living in a peaceful one. The severity of the shock is measured through the frequency, temporal spacing, and spatial distribution of the event, and the way people affected perceive the shock [2]. The frequency of shocks represents the number of events in a given period. The temporal spacing measures the elapsed time between two events. The spatial distribution takes into account the extent of the shock in a given region; for instance, an event that is isolated to a specific area is easier to deal with than an event that affects an entire country. Finally, the way people perceive the shocks is shaped by expectations and experiences from previous events.

The role of vulnerability and severity is highlighted in the case of Bangladesh over the period 1994–2010. Moderate flooding, as compared to low levels of flooding, increased an individual’s likelihood to move locally, but decreased his or her likelihood to make a long-distance migration; this was especially true for vulnerable groups such as the poor or women. Moreover, households that were not directly affected by the flooding but lived in areas with severe crop failure were more likely to move [3]. Figure 2 provides a good illustration of how a disaster’s severity impacts population displacement. It shows that displacements due to large-scale events represented 62% of displacement in 2010. This is mainly due to the fact that large-scale disasters occurred in 2010 with, for instance, the earthquakes in Haiti and Chile and significant floods in China, Columbia, Mexico, and Brazil. In 2014, just 32 large to very large-scale events (accounting for less than 5% of all globally recognized events) were the cause of 83% of total displacements. Meanwhile, very small to medium-sized events represented 95.4% of the total number of individual disasters but caused only 17% of the total number of displaced people (Figure 3). This shows that very small numbers of large-scale disasters can be responsible for a huge portion of the displacement, while most disasters, which are considered small- to medium-sized events, are responsible for far fewer displacements.

The role of remittances

Migration can also serve as a coping mechanism through the remittances sent back by emigrants to communities affected by climatic shocks and natural disasters. Remittances help increase the resilience of households toward natural disasters and reduce their vulnerability to the effects of shocks. As migrants are, by definition, not present in their home communities, their transfers provide insurance in case of shocks for their left-behind relatives. Consequently, remittances help households deal with income shocks caused by disasters.

An example from the Philippines shows that transfers of money back home from international migrants increase when natural disasters occur in their country of origin. Filipino households with overseas migrants managed to completely mitigate the income losses they suffered as a result of rainfall shocks with the receipt of remittances; this was not the case for households without overseas migrants [4]. In this context, it would thus be important to find ways to reduce the cost of sending remittances, which currently remain high, particularly in the case of international migrants’ transfers.

Internal vs international migration

Studies that look at the impact of climatic factors on internal migration use the urbanization rate, measured as a country’s share of urban to total population, as a proxy for rural–urban migration due to the unavailability of comparable internal migration data across countries and over time [5], [6]. This is based on the assumption that most internal population displacement is due to rural-urban migration. However, evidence on the link between climate change, natural disasters, and internal migration is rather mixed and varies depending on the nature of the shock and across regions. On the one hand, it has been found that natural disasters, defined as short-term shocks, increase the urbanization rate in developing countries [6]. On the other hand, evidence shows that increasing temperatures, associated with long-term events, positively affect internal migration in middle-income countries but not in low-income countries, which is related to liquidity constraints, as will be discussed later in the article [5].

Evidence also shows that climatic shocks and natural disasters could lead to international migration [1], [7], [8]. For instance, natural disasters closely related to climate change such as storms, floods, wet mass movements, drought, wildfire, and extreme high temperatures, have been shown to boost migration from developing countries to the six main OECD receiving countries: Australia, Canada, France, Germany, the UK, and the US. Furthermore, this effect is primarily driven by the migration of highly educated people to these countries [1]. Education is correlated with income, which may indicate that those highly educated people can afford migration costs. This could also be interpreted to mean that disasters related to climate change lead to brain drain from developing countries, especially when the affected countries are in a vulnerable situation due to the shock.

Another body of evidence finds that climatic shocks such as weather anomalies affect international migration through their effect on internal migration, which is called an “economic geographic channel” [8]. For instance, in the case of sub-Saharan Africa, weather anomalies are positively associated with rural–urban migration because of their effects on the agricultural sector. This internal migration, in turn, leads to an increase in international migration because it raises the number of workers in cities, translating into lower wages and increasing people’s willingness to move internationally in search of higher wages. Weather anomalies can also lead to high international migration through a so-called “amenity channel” by increasing the spread of disease and risk of death [8].

The role of liquidity constraints: Slow vs rapid onsets and temporary vs permanent migration

The positive relationship between climatic shocks and migration, both internal and international, has been challenged in the economics literature. There is some evidence showing that climatic shocks do not necessarily lead to more internal or international migration if the affected people are burdened by liquidity constraints or if they have to deal with slow onset events such as slowly changing temperatures [5]. Conversely, it might be argued that when faced with rapid onset events such as cyclones, storms, and floods, people could be forced to move because they lose everything all at once, which is not necessarily the case with slow onset events. Moreover, studies show that due to liquidity constraints, victims of rapid onset events are more likely than victims of slow onset events to make short-distance migrations [6] or short-term relocations, rather than to embark on permanent or long-distance migration [3]. For instance, a large-scale analysis from Indonesia illustrates the impact of long-term climatic shocks versus short-term disasters on different types of migration. Considering internal migration (i.e. province-to-province migration) of more than 7,000 households over 15 years, this study showed that natural disasters, which can also be considered as rapid and sudden events, only have a marginal effect on permanent outmigration to another province, while climatic variations associated with slow onset events such as rainfall and temperature variations increase permanent outmigration from a certain threshold (25°C for temperature and 2.2m for rainfall), with the effect of high temperatures being more important than that of greater rainfall [9].